1. Field of the Invention
The invention relates to a method of contrast correction of color television signals.
In color television, small contrast differences which are present in the dark parts of a scene are not transmitted clearly enough, and, as is known, the video signal transmission path therefore incorporates circuit arrangements the stretching the amplitude of the video signals in these dark parts. These circuit arrangements are known as black stretching circuits.
In addition to the known and conventional gamma correction for adapting the linear opto-electronic pick-up characteristic to the non-linear electro-optical display characteristic, this additional contrast correction is also efficient because it can compensate for the limited magnitude of contrast in television pick-up and display apparatuses when pictures or natural scenes which are rich in contrast are processed.
2. Description of the Related Art
A circuit arrangement for contrast correction or black stretching is known from DE 28 55 189 A1, corresponding to U.S. Pat. No. 4,241,362, in which, after connection, a correction signal derived from a gamma-corrected luminance signal can be superimposed on the luminance signal. This known circuit arrangement has the drawback that it may generate unwanted step-shaped jumps in brightness in the contrast-corrected luminance signal.